Every year around the globe a number of people are killed by tornadoes which are deadly air funnels with winds moving at 100 to 250 miles per hour. Tornadoes travel forward at an average speed of 35 miles per hour and their paths have an average width of 141 yards (The Audubon Society Field Guide to North American Weather by David M.Ludlum, published by Alfred A. Knopf, New York, 1991). Because of their awesome destructive power, when a tornado is sited it is important for human beings to get into a strong protective shelter fast. The invention to be described here is just such a tornado shelter.
A survey of prior art in the field of tornado shelters reveals the following. U.S. Pat. No. 302,463 issued to Francis K. Alexander in 1884, entitled "Tornado Proof Building", discloses a cylindrical shaped building with a conical roof and a semi-conical flange at its base which is buried in the ground to provide extra stability. However, the said building is not prefabricated. It must be constructed at the site. Also it is not portable.
U.S. Pat. No. 592,190 issued to Richard T. Bond in 1897, entitled, "Cyclone Refuge", discloses a generally cylindrical shelter which normally sits above ground but which may be lowered by a winch and ropes into a cylindrical hole in the ground when a cyclone or tornado is imminent. The shelter itself might be prefabricated, but its protective hole and the hole's lining must be constructed at the site and is not portable.
U.S. Pat. No. 4,126,972 for a "Tornado Protection Building" issued to Almer Silen in 1978 discloses a box-shaped metal-walled room with reinforcement beams in the walls and steal girders at its base which are firmly anchored in the foundational concrete slab of a house in which the said room is located. This shelter is meant to be constructed at site inside a house without a basement. It is neither prefabricated nor portable.
U.S. Pat. No. 4,615,158 for a "Mobile Home Tornado Shelter" issued to Sandra K. Thorton in 1986 discloses a cylindrically shaped shelter that is buried in the ground and which contains a passageway for access directly into the shelter from the mobile home. It is pointed out here that mobile homes have neither basements nor are they wind resistant enough to withstand the destructive force of a tornado. This shelter may be prefabricated but it is not portable.
U.S. Pat. No. 4,955,166 for a "Tornado Underground Shelter" issued to Steve M. Qualine and Louis R. Dunnam in 1990 discloses a prefabricated trucated globe-shaped shelter which is buried in the ground and contains a short stairway and door leading to the surface of the ground. Although it is prefabricated, once the shelter is buried in the ground, it is no longer portable.
In view of the prior art, it was an object of the present inventor to design a tornado shelter that was simple, inexpensive, prefabricated, easy to assemble and to disassemble, and portable. These objects were accomplished in the present invention to be described herein.